Aspects of the present invention relate to systems and methods for automatically controlling the direction and speed of movement of a vehicle, such as on a roadway. Further aspects of the invention relate to systems and methods for determining the position of a moving vehicle relative to other moving vehicles and non-moving objects, such as on a roadway.
The development of an automobile or other motor vehicle that can maneuver itself safely on a public roadway without a human operator is a goal that has been sought for a very long time, perhaps from the time of the automobile's very invention. Many other forms of transportation already include self-piloting mechanisms, such as airplanes, ships and a few light rail systems found in airports. Progress demands that the tiresome chore of driving give way to leisurely rides in cars that drive themselves. Popular science fiction, periodicals, television, and movies describe future worlds where automobiles, trucks, buses and other motorized vehicles are fully automated, ferrying passengers from point to point over public roadways, all without the aid of a human operator. However, many obstacles remain before the goal can be attained. Achieving the goal requires a man-made system to autonomously perform that which previously required a combination of complex human perception, reliable judgment and action.
One part of the challenge is to develop a system which reliably determines the position of a moving vehicle with respect to other moving vehicles. Such system must also reliably determine the position of the moving vehicle with respect to the changing contour of the roadway, e.g., the shifting positions of the roadway's boundaries and lane markings. One known system for determining a vehicle's position is a global positioning satellite (“GPS”) receiver. A GPS receiver, by simultaneously receiving signals from several space satellites orbiting the earth, can determine one's position anywhere on the earth. By analyzing measurements taken over a period of time, a GPS receiver can also estimate one's speed. The GPS system has both civilian and military aspects. Military GPS receivers receive special military-only GPS signals to guide objects with the highest precision. Civilian GPS receivers are less precise. At best, civilian GPS receivers have measurement errors of several feet or more, certainly too great to rely on individual GPS receivers alone to prevent vehicles in adjacent lanes of a roadway from colliding.
As described in U.S. Pat. No. 4,486,694, one way of guiding a driverless vehicle involves “detecting a magnetic field generated by a guide path, such as a conductor wire energized by a high frequency current.” (col. 1, Ins. 15-17). One or more energized linearly extending conductive guide wires are required to run the entire length of the route. It is apparent that such guiding method is not suitable for widespread implementation. Providing energized guide wires involves formidable expense and requires a long-term undertaking to retrofit even a minority of the most heavily trafficked roads. The costs and logistics of adding energized wires to roads makes it likely that only a few roads would ever be so equipped. Systems that require energized guide paths to function lead to a technological dead end. Such systems do not provide a migration path to future driverless vehicle systems because they are not compatible with existing roadways and their use by today's human-operated vehicles.